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Fusion Science and Technology
Trump leaves space nuclear policy executive order for Biden team
A hot fire test of the core stage for NASA’s Space Launch System rocket at Stennis Space Center in Mississippi was not completed as planned. The SLS is the vehicle meant to propel a crewed mission to the moon in 2024. Source: NASA Television
Among the executive orders President Trump issued during his last weeks in office was “Promoting Small Modular Reactors for National Defense and Space Exploration,” which builds on the Space Policy Directives published during his term. The order, issued on January 12, calls for actions within the next six months by NASA and the Department of Defense (DOD), together with the Department of Energy and other federal entities. Whether the Biden administration will retain some, all, or none of the specific goals of the Trump administration’s space nuclear policy remains to be seen, but one thing is very clear: If deep space exploration remains a priority, nuclear-powered and -propelled spacecraft will be needed.
The prospects for near-term deployment of nuclear propulsion and power systems in space improved during Trump’s presidency. However, Trump left office days after a hot fire test of NASA’s Space Launch System (SLS) rocket did not go as planned. The SLS rocket is meant to propel crewed missions to the moon in 2024 and to enable a series of long-duration lunar missions that could be powered by small lunar reactor installations. The test on January 16 of four engines that were supposed to fire for over eight minutes was automatically aborted after one minute, casting some doubt that a planned November 2021 Artemis I mission can go ahead on schedule.
H. Takenaga, H. Kawashima, S. Nishio, K. Tobita
Fusion Science and Technology | Volume 57 | Number 1 | January 2010 | Pages 94-102
Technical Paper | dx.doi.org/10.13182/FST10-A9270
Articles are hosted by Taylor and Francis Online.
A fueling scenario in a fusion reactor has been investigated, where tritium is fueled in the main plasma and deuterium is fueled in both the main plasma and the edge plasma. The tritium fueling in the main plasma minimizes the tritium fueling rate necessary for sustaining the high tritium density in the main plasma, resulting in the minimum tritium recycling level at the fixed pumping fraction. The deuterium fueling in the main plasma sustains the high deuterium density in the main plasma, and the deuterium fueling in the edge plasma enhances the deuterium recycling level for reducing the divertor temperature. Based on this scenario, particle balance was quantitatively investigated using the SlimCS design parameters at 2.95-GW fusion output with consideration of confinement times separately estimated for the particles fueled in the main plasma and the edge plasma. The fueling rates in the main plasma were evaluated to be 2.5 × 1022/s for tritium and 1.4 × 1022/s for deuterium when the confinement times for the particles fueled in the main and edge plasmas were assumed to be 2 s and 2 ms, respectively, and the divertor pumping fraction was assumed to be 3% of the particle flux to the divertor plates. For enhancement of the recycling level, the additional deuterium fueling in the edge plasma of 3.6 × 1023/s was required in this case. In order to satisfy the tritium balance, it was necessary to suppress the tritium retention rate to <0.01% of the tritium recycling rate and the tritium loss in the tritium cycle system to below 0.2% of the tritium fueling rate with the tritium breeding ratio of 1.05.